The same process, this time due to an attack from the immune system, damages nerves in the brain and results in MS.

Loud noises are well known to lead to hearing problems such as
temporary deafness or tinnitus (ringing in the ears). But this is the
first time scientists have been able to identify the underlying damage
to nerve cells.

The findings are published in the journal Proceedings of the National Academy of Sciences.

Lead researcher Dr Martine Hamann, from the University of
Leicester, said "The research allows us to understand the pathway from
exposure to loud noises to hearing loss. Dissecting the cellular
mechanisms underlying this condition is likely to bring a very
significant healthcare benefit to a wide population. The work will help
prevention as well as progression into finding appropriate cures for
hearing loss."

The scientists found that myelin lost as a result of noise exposure regrows in time, meaning hearing can recover.

"We now understand why hearing loss can be reversible in certain
cases," Dr Hamann added. "We showed that the sheath around the auditory
nerve is lost in about half of the cells we looked at, a bit like
stripping the electrical cable linking an amplifier to the loudspeaker.
The effect is reversible and after three months, hearing has recovered
and so has the sheath around the auditory nerve."

The work is part of ongoing research into the effects of loud
noises on the cochlea nucleus, a brainstem region that receives sound
signals from the inner ear.

The team has already shown that damage to cells in the cochlea nucleus can cause tinnitus.